Method of finning



June 9, 1942. A. w. GAY

METHOD OF FINNING "Filed Oct. 24. 1940 2 Shee'Es-Sheet 1 R v 0 W n I? AU June 9, 1942. A. w. GAY

METHOD OF FINNING' Filed Oct. 24, 1940 2 Sheets-Sheet 2 INVENTOR.flerwut V14 64 Y ATTORNEY.

Patented June 9, 1942 UNITED STATES PATENT OFFICE ME'rnonoF FINNINGArthur W. Gay, Akron, Ohio Application October 24,1940, Serial No.362,58ll ((122-204) 12 Claims.

, of a cylinder barrel of an air-cooled internal combustion engine ofthe type commonly employed in the aircraft industry, where rapid andeflicient heat dissipation is required to minimize engine efiiciencylosses and the failure of engine parts due to operation at unduly hightemperatures. Dissipation of the heat rapidly enough from the cylinderbarrel so that the temperature of the engine will not become such, as toadversely afiect its operating efilciency, can be accomplished only ifthere is a free and unimpeded fiow of heat from the wall of the cylinderbarrel into the fins.

Various methods have been employed hereto-- fore for providing suchcylinder barrels with cooling fins. These methods have included themanufacture of cylinder barrels with integral cooling fins, either bycasting them as a part of the barrel or providing the barrelwithsufilcient wall thickness so that fins could be machined therein. Ithas been found that there were many undesirable features inherent inbarrels with integral fins, among which were the inability of thelimited heat dissipating surface areas provided on these barrels toeffect an adequate or desired cooling of the engine; poor thermalconductivity of the material comprising the cylinder barrel and thefins; excessive weight of the barrel if an attempt were made to obtainsuficient cooling surface area by enlarging or spacing the fins closertogether; and a relatively high cost of manufacture. Another method offirming barrels embodied the use of preformed fins. Where such fins wereemployed and secured to the cylin- .der barrel by any of the well-knownmethods,

such as shrinking, soldering, brazing, welding, or the like, it wasfound that these methods were not particularly acceptable to theproduction '01 finned cylinder barrels for use in airc'raftenglnes.Although sumcient heat dissipating surface area could be obtained, itwas ineffective due to the unreliability and poor thermal conductivityof the Joint between the barrel and the fins, which precluded a rapid orfree flow of heat thereacross.

Furthermore, the joint was not strong enough result that the fins becameloosened or separated from the cylinder barrel. Nor were mechanicalweaknesses and poor conductivity the only disadvantages resulting fromthe use of soldering,

brazing, or welding. Where the barrel was made of a special alloy, theheat attending the practice of these processes seriously afiectedessential characteristics of the metal comprising the barrel orprecluded the use of certain desirable metals for the preformed coolingfins.

The present invention embodies a new and improved method of producingcylinder barrels for internal combustion engines with preformed coolingfins made of a metal having relatively high thermal conductivity, theproduct produced thereby being free from substantially all of theaforementioned drawbacks of cylinder barrels produced by priorpractices. The amount of e!- fective heat dissipating surface area canbe increased to any desirable amount with minimum increase in the weightof the engine member. The Joint between the cooling fins and thecylinder barrel is substantially free from insulating mediums andpermits the free flow of heat from the cylinder barrel to the coolingfins; moreover, the finned barrel can withstand severe serviceconditions without the this becoming detached or separated from thebarrel. These advantages are all attained without any undue or excessivecost in manufacture.

The method of the present invention for producing an article embodyingthe invention, may be briefly described as including the steps ofplacinga metal coating on that portion of the outer wall of the cylinder barrelto which the cooling fins are to be attached, assembling preformed finmembers in spaced relation to the coated portion of the cylinder barrel,heating the assembled fins and barrel to difierent predeterminedtemperatures and then securing the fin members to the outer surface ofthe barrel wall by casting preferably a metallic mull or sleeve aboutthe barrel, the mull being bonded to the wall of the barrel with theinner edge portions of the fins secured thereto.

Various objects and advantageous features of the invention not at thistime more particularly to withstand severe service conditions, with theB5 enumerated, will'become more apparent as the nature of the inventionis better understood from the following detailed description taken incon- Junction -with the' accompanying drawings,

present invention,

Figure 2 is a sectional view taken on the line 2-2 of Figure 1,

Figure 3 is an enlarged fragmentary sectional view taken on the line 3-3of Figure 2, Figure 4 is a fragmentary side elevational view partly insection of apparatus which may be employed for securing preformed finsto cylinder barrels in accordance with the teachings of the Figure 5 isan enlarged fragmentary top plan view of the apparatus illustrated inFigure Figure 6 is a sectional view, taken on the line 6-6 of Figure 5,and

Figure '7 is a fragmentary sectional detail of the apparatus.

With reference to Figures 1 to 3, inclusive, of the drawings, thenumeral 10 designates a cylinder barrel of an' air-cooled internalcombustion engine having the usual hold-down flange ll,

and threads l2, onto which the cylinder head (not shown) is threaded andshrunk in the usual manner. The outer surface of the barrel is providedwith a plurality of preformed relatively thin cooling fins I3, the inneredge portions of which are embedded in a cast muff H, which is bonded tothe exterior wall of the cylinder barrel. I

' The joint between the wall of the cylinder 10 and the muff I4, ischaracterized by having high thermal conductivity thereacross. Thenumber, size, and distribution of the fins mounted on the exterior ofthe barrel wall can be varied to provide sufficient heat dissipatingsurface area to 'meet the desired cooling requirements of the particularcylinder barrel. Although the fin members may be made of any suitablemetal having high thermal conductivity, I have found that where thecombination of lightness and rapid heat dissipation is particularlydesired in the fin ished article, aluminum has proven to be the mostacceptable for the fins l3 and muff II.

More particularly, the new and improved method of the present inventionfor providing -,to insure complete filling of the cavity and a porosityfree mud. The barrel is then cooled this point it is removed from thebath and rotation is continued in a horizontal position at a speedsufiicient to maintain the coating metal uniformly distributed over thesurface of the barrel until it has solidified. When the thus treatedbarrel is cooled, the metal coating can be freed of any adherentparticles of fiux and other foreign material by wire brushing under astream of water. It has been found that by this method a substantialcoating is applied on the barrel and it is desirable in certain cases toremove a portion thereof by taking a lathe cut on the coated surface ofthe barrel.

The preformed fins, w,hich may or may not have the inner edge portionstreated with a high melting aluminum solder, are assembled in a suitablemold or fixture and the assembly heated to a predetermined temperaturepreferably between 1000 F. and 1060 F. During the time that theassembled mold and fins are being heated to the desired temperature, thetreated barrel is also heated to a predetermined temperature,

preferably between 500 F. and 550 F. When the barrel and the mold havebeen heated to their respective predetermined temperatures, the barrelis inserted within the mold and the assembly prepared for casting themufi. The barrel is so disposed within the mold that the fins carried bythe mold are positioned in proper spaced relation along the coatedportion of the barrel wall. Molten aluminum is cast into the cavitydefined by the inner edge portions of the fins and the barrel wall,completely filling the same. The molten aluminum may be cast, underpressure with certain types of apparatus, or it may be cast by gravityfeed. In either casewthe mold assembly is vibrated during the ,ksastingoperation to approximately room temperature, removed from the mold,degated, trimmed, and is then cylinder barrels with preformed coolingfins mounted on the exterior surface thereof, consists of first cleaningthat portion of the exterior surface of the barrel which is to receivethe fins. Such cleaning-includes the heating of the barrel to apredetermined temperature, preferably between 500 F. and 600 F., untilall organic or volatile substances are removed. When the barrel hassufficiently cooled, that portion of the barrel to be finned is thenpolished or given a lightlathe cut to remove the extraneous matter onthe surface caused by the previous heating.

The surfaces of the barrel, except that to which the fins are to besubsequently applied, is covered with a film of masking material such asa chromic acid solution which is baked on the barrel at a temperature ofbetween 250 F.

and 300 F., to protect or mask such surfaces during the subsequentcoating and finning operations. When the barrel has become sufiicientlycool, the outer wall portion to be finned is apparatus includes acylindrical mold portion ready to be provided with a coating of arelatively low melting metal, which is preferably'zinc or an alloy ofzinc.

In applying this coating the barrel wall is wetted with a saturatedaqueous solution of zinc chloride. The barrel is then introduced into ametallizing bathand continuously rotated while immersed therein. Thebarrel is disposed within the bath, which is covered with a coating ofmolten zinc chloride, until it has reached a temperature'equal to thetemperature of the metal bath, preferably between 825 F. and 850 F. At

broadly indicated by the numeral 20 which serves to position thepreformed ring-like fin members 93 with respect to the barrel I0 duringthe casting of the muff I4. The mold portion 20 is preferably formed inquadrants, each of which consists of an arcuate base member'2l and anarcuate collar 22, interconnected by means of vertical posts 23 and 24.The lower ends of the posts 23 and 24 seat in spaced-bores 25 formed inthe base member 2| and are maintained therein by pins 28 traversing thebores 25 and engaging the posts 23 and 24. Similarly the upper ends ofthe posts 23 and 24 extend through openings 21 in the.

collar segment 22 and are secured therein by means of the pins 28.],

Between the collar segment 22 and the base member 2 I are disposed instacked relation a plu-, rality of arcuate spacers 30 having notchedcorners 3| which engage about the posts 23. The spacers 30 are freelymoveable along the posts 23 and and are adapted to receive them betweenthe fin members If. The thickness of v the spacers roughly determinesthe space between adjacent fins. However, the collar segment 22 isspaced from the base segment a distance slightly greater than the totalthickness of the fins and spacers to allow for expansion during thecasting operation, and the subsequent removal of the spacers. When thequadrants are positionedabout a barrel the edges of the spacers and thefin members are spaced from the barrel and define a mold cavity 32 intowhich molten aluminum is cast to form the muff.

The base quadrants 2| are provided with downwardly, outwardly inclinedinner surfaces 34 which in conjunction with the adjacent barrel walldefine an enlarged space about the barrel which serves as a circulargate for directing the molten metal into the mold cavity 32. The lowersurface of the quadrants 2! are provided with a peripheral cut-awayportion which receives the upwardly extending flange 31 formed on theupper surface 36 of a bottom gate casting 35. The surface 38 and theflange 31 are adapted which includes the steps of providing that portionof the exterior of a cylinder barrel which A is to receive the fins,with a coating of a metal alloy having a relatively. low melting point,as-

sembling ring-like aluminum fin members in.

- cylinder barrel wall which is to receive the fins with a bonding metalor metal-alloy having a relatively low melting point, assemblingring-like aluminum fin members in a mold and heating the same to apredetermined temperature, a

U mounting the barrel within said mold and then to receive, position,and support the quadrants of the mold portion 20. Mounted on the upperend of the mold portion 24 and serving to maintain the, collar quadrantsthereof in proper assembled relation, is a ring 42 which is providedwith a down-turned flange 43 seating within a a peripheral cut-awayportion of the collar segments 22.

The bottom gate casting 3' is provided with a cup-shaped. interior 3|terminating in acen-' tral opening 3! through the base thereof. Mountedwithin the member SI is-a closure member 48 having'an outer surfacespaced from the surface 38 and cooperating therewith to define acontinuance of-the circular gate. The closure member 48 is provided witha flange 49 which is adapted to extend into the lower end of thebarrelIt. The member 46 is maintained in proper position with respect to theend of the barrel by means of a bolt 41 which extends downwardly throughthe interior of the barrel. The upper end of the bolt 41 extends betweenspaced frame members 50 engaging theend of the barrel and receives theadjusting nut I.

For clamping the unit together there is provided hook members I2, thelower ends of which are adapted to engage the bottom of the member 88and the opposite ends are threaded to receive tightening nuts 53 whichengage plates I4 extending across the extremities of the frame members50.

The opening 39 in the'gate casting is adapted to receive'the upper endof a conduit 60 extendingupwardly' from the bottom of a ladle 8|normally filled with molten metal at a predetermined castingtemperature. metal is conveyed from the ladle Si by means of gaspressure exerted on the-surface of the molten metal. The gas underpressure is introduced into the ladle through the connection I! which isconnected to a suitable supply by means of conduit 63.

Having thus described my invention so that those skilled in the art maybe able to understand and practice the same, what I desire to obtain byLetters Patent is defined in the appended claims.

I claim:

1 The method of producing a cylinder barrel of a; ferrous metal alloyfor an air-cooled internal combustion engimr'withpreformed aluminumcooling fins on the exterior surface thereof securing the fin members'tothe barrel by casting an aluminum sleeve about said barrel, said sleevebeing bonded to the wall of the cylinder barrel and having the inneredge'portions of thefin members. secured thereto. 1 I

3. The method of producing a cylinder barrel of a ferrous metal alloyfor an air-cooled inter nal combustion engine with preformed coolingfins on theexterior surface thereof which in-' cludes the stepsofassembling ring-like, aluminum fin members in a mold and heating sameto a temperature of between 1000 F. and 1060 F.,' heating a cylinderbarrel to a temperature of between 500"F. and550 F. and. then securingthe fin members to the barrel by casting an aluminum sleeve about-saidbarrel, said sleeve being bonded to the wall of the cylinder barrel andhaving the inner edge portions of the fins embedded therein. 4. Themethod of producing a cylinder bar- -rel of a, ferrous metal alloy for'an'air-cooled internalcombustion engine with preformed cooling fins onthe exterior surface thereof which includes the steps of applying ametallic coating to that portion of a barrel wall which is to receivethe fins, assembling ring-like aluminum fin members in a mold andheating same to,

a temperature of between 1000 F. and 1060 F.,

heating the coated barrel to a temperature ofbetween 500 F. and 550 F.,assembling thebarrel within the mold and then securing the fin membersto the barrel by casting an aluminum sleeve about said barrel, saidsleeve being bonded to the wall of thecylinder barrel and having the finmembers embedded therein.

5. The method of producing a cylinder barrel of a ferrous metal alloyfor an air-cooled inter- The molten nal combustion engine with preformedcooling fins on the exterior surface thereof which includes the steps ofapplying a metallic coating to the exterior wall portion of a cylinderbarrel, assembling ring-like aluminum fin members in spaced relationalong the coated portion of the barrel and forming therewith a castingcavity, securing the inner edge portions of the fins to the barrel wallby casting metal into the casting cavity, and vibrating the barrel andmold assembly during the casting operation.

6. The method of producing a cylinder barrel of a ferrous metal alloyfor an air-cooled internal combustion engine with preformed cooling finson the exterior surface thereof which includes the steps of applying ametallic coating to that portion of acylinder barrel wall which is toreceive the preformed fins, heating thebar- I relto a predeterminedtemperature, assembling the barrel in a moldcontaining preformedringlike aluminum fin members, casting molten metal into the cavityformed between the barrel wall and the mold to secure the fin members tothe barrel wall, and vibrating the barrel and mold assembly during thecasting of the metal.

7. The method of producing a cylinder barrel of a ferrous metal alloyfor an air-cooled internal combustion engine with preformed aluminumcooling fins on the exterior surface thereof which includes the steps ofapplying a metal coating to that portion of a cylinder barrel wall whichis to receive the preformed fins, heating the barrel to a predeterminedtemperature, simultaneouslyheating a mold assembly containing preformedfin members to a different predetermined tem- 3 perature, positioningthe heated barrel within the mold assembly and castingmolten metal intothe cavity formedbetween the barrel wall and the mold to secure the finmembers to the barrel wall, and vibrating the barrel and mold assemblyduring the casting of the metal;

8. The method of producing a cylinder barrel of a ferrous metal alloyfor an air-cooled internal combustion engine with preformed cooling finson the exterior surface thereof which includes the steps of applying ametal coating to that portion of a cylinder barrel wall which is toreceive the preformed fins, heating the barrel to a temperature ofbetween 500 F. and 550 F, simultaneously heating a'mold assemblyincluding preformed ring-like aluminum fins to a temperature of between1000 F. and 1060 F., posifins on the exterior surface thereof whichincludes the steps of cleaning the wall of a cylinder barrel to providea surface free of all volatile or extraneous matter, applying arelatively thin metallic coating to said surface, heating the barrel toa temperature of between 500 F. and 550 F., simultaneously heating amold assembly ineluding preformed aluminum fins to a temperature ofbetween 1000 F. and 1060 F., positioning the barrel within the moldassembly and casting molten aluminum into the cavity defined by thebarrel wall and the mold to secure the fins to the barrel'wall. r

10'. The method of producing a cylinder barrel of a ferrous metal alloyfor an air-cooled internal combustion engine with preformed cooling finson the exterior surface thereof which includes the steps of cleaning theexterior wall. of a cylinder barrel to provide a surface free of allvolatile or extraneous matter, applying a relatively thin metalliccoating to said surface, heating the barrel to a temperature of between500 F. and 550 F., simultaneously heating a mold assembly includingpreformed aluminum fins to a temperature of between 1000 F; and 1060 F.,positioning the barrel within the mold assembly and casting moltenaluminum into the cavity defined by the barrel wall and the mold tosecure the fins to the barrel wall, and vibrating the mold assembly andbarrel during the casting of the metal.

11. The method of producing a cylinder barrel of a ferrous metal alloyfor an air-cooled internal combustion engine with preformed cooling finson the exterior surface thereof which includes the steps of cleaning'theexterior wall of a cylinder barrel to provide a surface free of allvolatile or extraneous matter, applying a relatively thin metalliccoating to-said surface, heating the barrel to a temperature of between500 F. and 550 F., simultaneously heating a mold assembly includingpreformed aluminum fins to a temperature of 1000'F. to 1060 F., mountingthe barrel: within said mold and then securing the fin members to thebarrel by casting a sleeve about said barrel, said sleeve being bondedto the wall of the cylinder barrel and having the inner edge portions ofthe fin members imbedded therein. I

12. The method of producing a cylinder barrel of a ferrous metal alloyfor an air-cooled internal combustion engine with preformed cooling finson the exterior surface thereof which includes the steps of cleaning theexterior wall of a cylinder barrel to provide a surface free of'allvolatile or extraneous matter, applying a relatively thin metalliccoating to said surface comprising a zinc alloy, heating the barrel to atemperature of-between 500 F. and. 550 F., simultaneously heating a moldassembly including preformed-aluminum fins to a temperature of 1000" F.to 1060 F., mounting the barrel within said mold,- securing the finmembers to the barrel by casting a sleeve about said barrel, andvibrating the mold assembly and barrel during the casting operation,said sleeve being bonded to the wall of the cylinder barrel and havingthe inner edge portions of the fin members embedded therein. ARTHUR W.GAY.

